It is a little bit past the big V-Day, but some good almost free ideas:
A box of dates: Write down a bunch of date ideas on slips of paper. ("One night out to a movie of your choice," "One dinner date at a restaurant of your choice.") put them all in a box and wrap up the box.
Personally, this is what I did for my boyfriend this year. I bought a pack of blank cards in the scrapbooking aisle at Target, wrote clues on them as to what we would be doing that evening and hid them where I knew he would find them at different times of the day. They all lead up to a dinner out at a favorite (but cheaper) restaurant that we went on our first date.